The principal objective of the Biostatistics Core will be to provide project investigators a centralized resource for biostatistics expertise. Statistical issues will be addressed at all levels of investigation: from the design of experiments, to the maintenance of data quality; and from conclusions based on formal hypothesis testing, to important leads discovered by thorough data exploration. In support of this objective, the specific aims of the Core include: 1. Collaborate with project investigators in the formulation of unambiguous hypotheses and hypothesis testing strategies, and in the design of experiments and population studies. 2. Provide support for all projects with: formal hypothesis tests in experimental data that ensure strong conclusions; exploratory analyses that lead to further experiments, refined hypotheses, or discoveries; frequent collaborative meetings about refining design, sample size, and resource use as evidence is accumulated; statistical modeling and sensitivity analyses of complex data; and visual displays of data that clarify conclusions and uncover leads. 3. Provide data transfer, management, and integration services that ensure high integrity, security and investigator accessibility. 4. Investigate new methodologies to directly address difficult data or design problems.